The goals of this proposed project are to identify mechanisms which regulate shape and size of virus components during morphogenesis and to develop improved methods for preserving subcellular components for structural analysis. Objectives are to study length determination in the tail tube of B. subtilis phage SP01 and coliphage T4 by in vitro assembly of purified baseplates and tube protein, and by complementation using extracts of mutant-infected cells. Studies on SP01 mutants will serve to test and extend the general validity of concepts derived from T4 results, and involve characterizing purified SP01 tail components by gel electrophoresis and electron microscopy. Head structure and assembly in T4 will be studied by characterizing newly isolated mutants in gene 40, by determining the ratios of protein components in headsize variants of T4, and by estimating the nature and extent of DNA organization in T4 by X-ray diffraction. Methods for preserving structure will be developed using protein crystals, crosslinking reagents, gel electrophoresis and combined electron microscopy and X-ray diffraction.